Fixation characteristics in macular disease. Relationship between saccadic frequency, sequencing, and reading rate.

The relationship between reading rate and saccadic frequency in patients with macular degeneration was studied to determine if this simple measure of eye movements would be helpful in explaining the reduction in reading rates. Nineteen subjects and five controls were tested for visual acuity, reading rate, and saccadic frequency for intended stationary, simple left-to-right, and sequencing step tasks. Eye movements were recorded using an electro-oculography technique. Absolute eye position was not known. The results demonstrated that, using a 2 degree threshold for a stationary target, patients refixated a mean of 42.7 times per min, and controls refixated 0.00 times per min. For a two-letter left-to-right task, patients averaged 3.57 times more saccades than an ideal response, and controls had 1.14 times more saccades than ideal (P less than 0.01). For a five-letter left-to-right sequencing task, patients refixated a mean of 2.10 times more than ideal, and controls refixated 1.15 times more than ideal (P less than 0.05). Regression analysis demonstrated that sequencing task scores of saccadic frequency and visual acuity were the best predictors of reading rate (r2 = 0.705). These results indicate that higher saccadic frequencies are associated with lower reading rates and that there appears to be a relationship between the sequencing of visual information and reading rate.